The present invention concerns fiber technology. It is, for example, readily applicable to woven and nonwoven fibrous materials. It concerns general techniques, methods and materials relating to degradable polymer fibers, especially those readily incorporated into woven and nonwoven products and substrates.
In recent years, attention has focused on preferred degradable polymers, which can be converted to desirable substrates or articles. Much of this attention is focused on polymers which include, as a monomeric unit therein, the result of lactic acid or lactide polymerization. Attention is directed, for example, to U.S. Pat. No. 5,525,701, the complete disclosures of which are incorporated herein by reference. It is noted that U.S. Pat. No. 5,525,706 is owned by Cargill Incorporated, of Minneapolis, Minn. Cargill Incorporated is the assignee of the present application as well.
Other published patents which concern polymers of lactic acid or lactide include: U.S. Pat. Nos. 5,444,113; 5,424,346; 5,216,050; European Publication No. 747065 A1; European Publication No. 723043 A2; French publication 2725731; and; European Publication No. 637641 A1.
Incorporation of such technology into preferred fibrous materials, especially in the generation of nonwoven fiber substrates, is a focus of concern herein.
The present invention relates to a fibrous material which includes a plurality of polylactide containing fibers. The plurality of polylactide containing fibers can be considered low shrinkage or high shrinkage. The plurality of polylactide containing fibers are considered low shrinkage fibers if they provide a boiling water shrinkage propensity of less than about 20%. The plurality of polylactide containing fibers are considered high shrink fibers if they provide an average fiber boiling water shrinkage propensity of greater than about 10% and a heat of fusion of less than about 25 J/g. The invention additionally relates to the use of extrusion processes to provide low shrinkage fibers and high shrinkage fibers. The invention further relates to the use of these fibers in desirable products.